The Sense of Hearing: The Ears

The ears have two types of receptors. They are phonoreceptor and statoresreceptor. Phonoreceptor receives the auditory stimuli and have the power to convert them into auditory impulses. Statoresreceptor control postural changes and changes the orientation of the body or balance. That is why ear is called not only the organ of hearing. There are external ear, the middle ear, and the internal ear.

1. The external ear:

   The external ear consists of two parts: pinna and external auditory canal.

   1. Pinna

      Pinna is funnel shaped and has ridges and grooves. Pinna is immovable and it is supported by an elastic cartilage which has a funnel-shaped aperture called concha. It collects and directs the sound waves by concha of the pinna to the external auditory canal.

   2. External auditory canal

      External auditory canal is an oblique and tubular canal which runs inward from the canal to the ear drum. The inner wall is provided with ceruminous glands. Its produces ear wax which protects the eardrum. It separates the external ear from the middle ear.

2. The middle ear

   The middle ear consists of an air filled cavity called tympanic cavity. that is connected to the pharynx by a eustachian tube. The tympanic membrane is oval, delicate membrane capable of vibrating. Tympanic cavity consists of 3 tiny bone called ear ossicles. They are incus, malleus, and stapes. Malleus is a hammer-shaped outer bone. The incus is an anvil-shaped middle bone.It articulates with the malleus on one side and stapes on other side. Stapes is an inner bone and attached to the internal ear.

3. The internal ear

   The internal ear consists of the vestibule, semicircular canal, and cochlea. The vestibule is a small rounded chamber that forms the central part of the internal ear. The vestibule consists of two delicate membranes, oval window and round window. Semicircular canals are three in numbers and they are mutually perpendicular to each other and form ampulla. It is directly concerned with the balance of the body and plays no part of the internal ear. The cochlea is spirally coiled like snail’s shell which receives the vibration of the sound. It is surrounded by the bony part called cochlear canal.

Working mechanism of ears

The external ear collects the sound waves and the sound waves passes into the auditory tube. The sound waves then enter the middle ear and strike the eardrum, ear oscicles and finally reach to the cochlea. Sound waves set the fluid of cochlea in motion. Due to which the auditory cells are activated. The stimulus or impulse is carried to the brain by the auditory nerves.

Care and protection of the ears

• We should not take out the earwax from ear normally. If it interferes the hearing, it should be taken out safely.
• We should not use sharp things like the tooth pick, key etc. to prick the ears.
• We should consult the doctor in case of pain, pus formation, bleeding etc. in ears.
• We should protect our ears from loud noisy sounds.
• We should not take out any foreign body from our ears that may enter our ears by different causes.